How to reassemble parts on Thread tension on Singer Industrial Machine?

Need a service manual for a Singer Treadle Sewing Machine Model 66-1?

Engine revving up ?

the thread is bunching on underside of fabric it looks like birdnest?

Singer 201 went bang , smelt and now won’t work?

My CG 500/550 Singer Sewing Machine's bobbin isn't working?

Singer 507?

Bobbin won't wind?

1965 Singer 275k sewing machine foot pedal?

Singer zigzag 457 Stylist not threading bobbin/making stitch?

Need an equivalent to an old Hunts WA71 capacitor/rectifier?

What size needles can I use for my Singer 39a3?

Presser foot is loose?